Summary: An ERN (Employer Reference Number) is a unique identifier issued by HMRC to employers operating a PAYE scheme. It’s made up of a 3-digit HMRC office code followed by a unique reference of up to 10 characters (e.g. 123/AB45678). You can find your ERN in your HMRC welcome pack, on P45 and P60 forms or payslips, or through your PAYE Online account. You’ll need it for payroll administration, filing RTI returns, and buying Employers’ Liability Insurance, and when employees need it for things like Universal Credit claims.
Starting and running a business is exciting—but the paperwork? Not so much. As an employer, compliance is key in every aspect, especially in payroll. In the sea of information business owners receive, one thing that often gets overlooked but is vital to successful operations is ERN numbers.
While it may not look like much, it’s key to everything from paying your staff to securing insurance.
Don’t know what your ERN is? Don’t worry, we’ll outline everything you need to know, from what an ERN number is, why it matters, and how to find (or avoid needing) one—without the headache.
What is an ERN number?
ERN numbers are a unique identifier given to each employer by HMRC (Her Majesty’s Revenue and Customs) when you register as an employer for Pay As You Earn (PAYE). This number is used for tax and payroll purposes, like when calculating tax for your employees.
It’s also known as the PAYE reference number, which you’ll see on payroll-related documents.
Not only are ERN numbers important for payroll administration, but they also come into play for tax compliance and employee verification, as well as for insurance purposes and accessing online services.
What does an ERN number look like?
Let’s break down what makes an ERN number so you can easily find it.
Your ERN number is a combination of a 3-digit HMRC number (this identifies the office that deals with your business) and a unique reference solely for your business, separated by a slash.
So, something like this: 123/AB45678
It’s worth noting that if your business was registered before 2001, it will look slightly different as ERN numbers after this gained an additional letter in the unique reference part—otherwise, it’s the same as above but with one less letter.
How do I find my ERN number?
You can find your employer reference number in several places:
- Inside the yellow welcome booklet supplied by HMRC when you first registered as an employer,
- Other communication from HMRC about PAYE,
- Alternatively, you can contact the HMRC employer’s helpline.
You won’t find your ERN on Companies House filings, VAT certificates, or business bank statements—it’s strictly tied to PAYE and payroll-related documents.
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Who needs an ERN?
You need an ERN if you:
- register as an employer with HMRC
- operate a PAYE scheme
- employ at least one person earning at or above the Lower Earnings Limit (£129 a week for 2026/27)
You’ll also need to register if any of your employees get expenses or benefits, have another job, or get a pension, even if they earn below the Lower Earnings Limit.
You don’t need an ERN if you:
- have no employees
- only work with self-employed contractors
- only have employees who are paid below the Lower Earnings Limit and don’t get expenses or benefits, have another job, or receive a pension
- are registered in Jersey, Guernsey, or the Isle of Man (which have their own systems)
As soon as you take on your first eligible employee, you’ll need to register with HMRC as an employer to get your ERN.
What are ERN numbers used for?
Employer reference numbers can be used in different ways. As an employer, you’ll need your ERN number as a tax reference number when completing end-of-year PAYE returns. If you were to input the wrong number, the claim would be rejected so it’s important to get this right!
Other times you’ll need your ERN number are:
- When completing any payroll-related paperwork; from payslips to P45s,
- Purchasing or renewing Employers’ Liability Insurance,
- And, at the request of employees to access their employment history or for applying for tax credits.
HMRC will also use your number for:
- Tax collection: HMRC will need your employer reference number to administer or collect any taxes surrounding your payroll. This includes National Insurance contributions and income tax. Your ERN number connects your payroll records to the PAYE scheme you are registered with.
- Compliance monitoring: As your unique number is linked to your payroll administration, it can be used by HMRC to track your payment history and ensure you are abiding by payroll and tax legislation. Paying an incorrect amount of tax or National Insurance, or submitting payroll-related paperwork late can result in enforcement action. Companies like Cintra can help to alleviate this possibility, automating processes and streamlining payments.
It’s worth noting that if you operate more than one PAYE scheme—for example, across different branches or legal entities—you may have multiple ERNs so make sure to use the correct ERN for each payroll submission!
ERN vs other business numbers
Employers often confuse their ERN with other reference numbers. Here’s how they differ:
| Reference number | Purpose | Issued by |
|---|---|---|
| ERN (Employer Reference Number) | PAYE tax and payroll administration | HMRC |
| Accounts Office reference | Making PAYE payments to HMRC | HMRC |
| UTR (Unique Taxpayer Reference) | Self Assessment and Corporation Tax | HMRC |
| Company registration number | Legal company identification | Companies House |
What is Employers’ Liability Insurance?
Employers’ Liability Insurance helps businesses to compensate employees in the event of an injury or work-related illness. It is a legal requirement under the Employers’ Liability Act 1969 and must start as soon as you become an employer.
By law, your ERN must appear on your Employer’ Liability Insurance certificate.
Making payroll understandable
Getting your head around the many different terms and legislations regarding payroll can be a challenge, especially in larger organisations. That’s where we come in.
Why not chat with one of our payroll professionals to see how we can help make your process stress-free, integrating seamlessly into your business? Book a demo to see how we e-rn our status as payroll pros.
Payroll Legislation Guide
The facts, figures, thresholds and allowances for 2026/27 spanning tax, National Insurance, pensions, statutory payments and more.
Frequently asked questions
Q. Is an ERN the same as a PAYE reference number?
A. Yes. ERN (Employer Reference Number) and PAYE reference number are two names for the same thing. You might also see it called your employer PAYE reference on HMRC letters and payroll documents.
Q. What’s the difference between an ERN and an Accounts Office reference?
A. Your ERN identifies your PAYE scheme, and you’ll use it for payroll submissions and paperwork. Your Accounts Office reference is a separate number you use when paying PAYE and National Insurance to HMRC. Both are issued when you register as an employer, so it’s easy to mix them up. Using the wrong one when making a payment can mean it isn’t matched to your account properly.
Q. When should I register for an ERN?
A. You’ll need to register as an employer before your first payday. You can register up to two months before you start paying people, so it’s worth doing it as soon as you know you’re hiring, to make sure your reference arrives in time.
Q. Does my ERN ever change?
A. Usually not. Your ERN stays the same for as long as you run the same PAYE scheme. You may get a new one if your business changes its legal structure, for example moving from sole trader to limited company, or if you set up a separate PAYE scheme for another part of your business.
Q. Do I need an ERN if I’m the only director being paid?
A. If you pay yourself a salary as a director at or above the Lower Earnings Limit (£129 a week for 2026/27), you’ll need to register as an employer and will get an ERN, even if you have no other staff.
Q. Why would an employee need my ERN?
A. Employees sometimes need it to fill in a Self Assessment tax return, check their employment history with HMRC, or support a Universal Credit claim. They can usually find it on their payslips, P60, or P45, but they may ask you for it directly.
Q. What should I do if I can’t find my ERN?
A. Check your HMRC welcome pack, any P60s or P45s you’ve issued, or your PAYE Online account. If you still can’t find it, call the HMRC employer helpline on 0300 200 3200 and they’ll help you.
